1. Field of the Invention
The present invention is generally related to an image sensor device and a manufacturing method thereof. More particularly, the present invention relates to an image sensor device and a manufacturing method thereof for preventing light leakage between different pixels and for reducing the focal length thereof.
2. Description of Related Art
Conventionally, a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) image sensor (CMOS Image Sensor, “CIS”) is used for a solid-state image sensor. A conventional CCD comprises a photodiode array, and pulsed voltage is applied to the charge stored by each photodiode, so as to output a corresponding electric signal. The CCD has the advantages of high dynamic range and low dark current; however, the cost is high and the manufacturing process is complicated. In recent years, CMOS image sensor has been well developed for being compatible with the manufacturing process of a CMOS transistor. Therefore, CMOS image sensor including a chip with a photodiode and a MOS transistor is used as a solid-state image sensor. A CMOS image sensor can be easily manufactured and the chip size thereof can be reduced. In addition, the CMOS image sensor can be easily integrated on a chip having other peripheral circuits, and thus the cost and the power consumption of an image sensor can be reduced. In general, a CMOS image sensor is preferable to a CCD in a low cost image sensing application.
FIG. 1 is a schematic cross-sectional view illustrating a conventional image sensor device. Referring to FIG. 1, a conventional image sensor device 100 includes a plurality of photo sensors 102, a plurality of active regions 104, a dielectric layer 106, an oxy-nitride layer 108, a plurality of color filters 110, a planar layer 112 and a plurality of microlenses 114. The photo sensors 102 include photodiodes. The photo sensors 102, the color filters 110 and the microlenses 114 are arranged as an array. The distance between the photo sensor 102 and the microlens 114 is represented as the focal length FL of the image sensor device 100.
In a solid-state image sensor such as CCD or CMOS image sensor described above, the problem of light leakage between different pixels is an important issue that may influence the photo sensitivity of the image sensor device. FIG. 2 schematically illustrates the crosstalk of the image sensor device shown in FIG. 1. Referring to FIG. 2, for example, the sensor 102a is used to receive the light 202 of the image. However, the light 204 incident from the neighboring pixels that has a large incident angle between the light 204 and the normal line N of the microlens 114 may be received by the sensor 102a. In addition, the light 206 incident from the gap between the color filters 110 may also be received by the sensor 102a. Furthermore, the image quality of the sensor 102a may be influenced by the scattering lights of the light 208 reflected from the active regions 104.
Accordingly, the color contrast of the image sensor device may be reduced by the crosstalk between the pixels of the image sensor device. Therefore, the photo sensitivity of the image is also reduced. Accordingly, an image sensor that can prevent light leakage between different pixels for resolving the problem of crosstalk is quite desirable.